Women Have Higher Risk of Fatal Stroke After Cardiac Surgery

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American Heart Association journal report:Women have higher risk of fatal stroke after cardiac surgery

DALLAS, May 1 -- Women are more likely to develop a stroke after cardiac surgery than men, and their strokes are more likely to be fatal, researchers report in today's Circulation: Journal of the American Heart Association.

Researchers looked at a number of possibilities to explain why women have a higher perioperative stroke risk -- smaller arteries, higher rates of high blood pressure, older age -- and concluded that female gender was an "independent" risk factor. Perioperative indicates the time period just before, during and shortly after surgery.

"There is something that predisposes women to stroke other than the traditionally known risk factors," says Charles W. Hogue, Jr., M.D., the first author of the paper, and an associate professor of anesthesiology and chief of the cardiothoracic anesthesiology division at Washington University School of Medicine in St. Louis.

The study included more than 400,000 individuals who underwent cardiac surgery in the United States during 1996 and 1997. Thirty-two percent of the patients were women. "We considered known risk factors including age, atherosclerosis, hypertension, diabetes and the types of cardiac surgery," says Hogue. "Even when we adjusted for all that, we found female gender was an independent risk factor for stroke after heart surgery."

The study has important implications for the future because of the nation's aging population, notes Victor G. D¥vila-Rom¥n, M.D., the paper's senior author and medical director of the Washington University Cardiovascular Imaging and Clinical Research Core Laboratory. The number of Americans age 65 and older is expected to rise from about 35 million today, to more than 78 million in 2050.

"This implies that the number of elderly patients and women undergoing cardiac surgery is also likely to double over the next 50 years," says D¥vila-Rom¥n. Currently, women make up about one-third of all heart surgery patients.

"More elderly patients are being referred for cardiac surgery, and these individuals are at high risk of developing postoperative complications such as stroke," he adds. "We should aggressively identify specific risk factors for these individuals to try to prevent strokes."

It is well known that women who have heart surgery fare worse than men, and that at all ages, women are more likely than men to die after cardiac surgery.

In 1999, Hogue, D¥vila-Rom¥n and colleagues reported results from a study of 3,000 patients. They found that being female was an independent risk factor for stroke immediately or within a few days after heart surgery. However, that study involved only patients treated at Washington University. The team set out to determine whether the finding held true throughout the nation.

They used data from the Society of Thoracic Surgery's National Cardiac Surgery Database, which contains results from operations conducted at a large number of academic and private practice facilities nationwide that do heart surgery.

The researchers identified 416,347 heart surgery patients who had either coronary artery bypass surgery and/or valve surgery and for whom complete neurological outcome information was available. New stroke occurred in 13,396 people, or 3.3 percent of the total population.

Women represented 32 percent of the population and had higher rates of stroke, ministrokes known as transient ischemic attacks, or coma due to a stroke than men. The perioperative stroke risk was 3.8 percent for women compared to 2.4 percent for men.

This higher frequency of stroke for women included all age groups and all types of cardiac surgical procedures, says Hogue. When they compared men and women who had experienced a stroke, the length of hospitalization was longer and the death rate was higher for women than for men. The death rate was 5.7 percent for women compared to 3.5 percent for men at 30 days following surgery. When the researchers accounted statistically for all known risk factors, women still had a 21 percent higher risk of stroke than men did.

Heart operations, particularly coronary bypass surgery, are relatively safe. Death rates have not increased much in the last 10 years, despite the fact that surgeons now operate on much older and sicker patients, he says.

"Even though the rate of postoperative stroke is relatively low, for those who suffer this complication after surgery, the implications can be devastating. The important implication of this study is that perioperative stroke, although uncommon, is a very serious complication of heart surgery," says D¥vila-Rom¥n. "One of our major goals is to create awareness that this is an important problem, particularly for women."

D¥vila-Rom¥n calls for aggressive strategies to prevent these types of strokes.

The study now adds stroke to the list of reasons why women have a poorer survival rate than men following heart surgery. It does not, however, shed light on why women have a higher risk. "The question is, what is unique about women that predisposes them to stroke," Hogue says.

One possible answer involves estrogen, the female sex hormone, he says. Animal studies suggest that estrogen can protect the brain against stroke. The sharp reduction in estrogen after menopause may help explain the higher perioperative stroke risk in women. "Most women who have heart surgery are postmenopausal," he says.

Co-authors are Benico Barzilai, M.D.; Karen S. Pieper, M.S.; Laura P. Coombs, Ph.D.; Elizabeth R. DeLong, Ph.D.; and Nicholas T. Kouchoukos, M.D.

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NR01-1285 (Circ/Hogue)Media Advisory: Dr. D¥vila-Rom¥n can be reached by phone at 314-362-4748; and by e-mail at [email protected]. Dr. Hogue can be reached by phone at 314-362-2538; and by e-mail at [email protected]. (Please do not publish contact information.)